Balsalazide disodium is indicated for the treatment of gastrointestinal diseases, for example mild to moderately active ulcerative colitis, radiation protosigmoidits, diverticulitis, irritable bowel syndrome (IBS) and colon cancer (see WO 95/18622). Balsalazide is a colon-specific, non-steroidal, anti-inflammatory aminosalicylate derivative. Balsalazide is also a prodrug containing 5-ASA, linked to 4-amino benzoyl-(3-alanine (“4-ABA”) by a diazo bond.